/**
 * @file llinterp.h
 *
 * $LicenseInfo:firstyear=2001&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_LLINTERP_H
#define LL_LLINTERP_H

#if defined(LL_WINDOWS)
// macro definitions for common math constants (e.g. M_PI) are declared under the _USE_MATH_DEFINES
// on Windows system.
// So, let's define _USE_MATH_DEFINES before including math.h
    #define _USE_MATH_DEFINES
#endif

#include "math.h"

// Class from which different types of interpolators can be derived

class LLInterpVal
{
public:
    virtual ~LLInterpVal() {}
};

template <typename Type>
class LLInterp
{
public:
        LLInterp();
    virtual ~LLInterp() {}

    virtual void start();
    virtual void update(const F32 time) = 0;
    const Type &getCurVal() const;

    void setStartVal(const Type &start_val);
    const Type &getStartVal() const;

    void setEndVal(const Type &target_val);
    const Type &getEndVal() const;

    void setStartTime(const F32 time);
    F32 getStartTime() const;

    void setEndTime(const F32 time);
    F32 getEndTime() const;

    bool isActive() const;
    bool isDone() const;

protected:
    F32 mStartTime;
    F32 mEndTime;
    F32 mDuration;
    bool mActive;
    bool mDone;

    Type mStartVal;
    Type mEndVal;

    F32 mCurTime;
    Type mCurVal;
};

template <typename Type>
class LLInterpLinear : public LLInterp<Type>
{
public:
    void start() override;
    void update(const F32 time) override;
    F32 getCurFrac() const;
protected:
    F32 mCurFrac;
};

template <typename Type>
class LLInterpExp : public LLInterpLinear<Type>
{
public:
    void update(const F32 time);
protected:
};

template <typename Type>
class LLInterpAttractor : public LLInterp<Type>
{
public:
    LLInterpAttractor();
    void start() override;
    void setStartVel(const Type &vel);
    void setForce(const F32 force);
    void update(const F32 time) override;
protected:
    F32 mForce;
    Type mStartVel;
    Type mVelocity;
};

template <typename Type>
class LLInterpFunc : public LLInterp<Type>
{
public:
    LLInterpFunc();
    void update(const F32 time) override;

    void setFunc(Type (*)(const F32, void *data), void *data);
protected:
    Type (*mFunc)(const F32 time, void *data);
    void *mData;
};


///////////////////////////////////
//
// Implementation
//
//

/////////////////////////////////
//
// LLInterp base class implementation
//

template <typename Type>
LLInterp<Type>::LLInterp()
: mStartVal(Type()), mEndVal(Type()), mCurVal(Type())
{
    mStartTime = 0.f;
    mEndTime = 1.f;
    mDuration = 1.f;
    mCurTime = 0.f;
    mDone = false;
    mActive = false;
}

template <class Type>
void LLInterp<Type>::setStartVal(const Type &start_val)
{
    mStartVal = start_val;
}

template <class Type>
void LLInterp<Type>::start()
{
    mCurVal = mStartVal;
    mCurTime = mStartTime;
    mDone = false;
    mActive = false;
}

template <class Type>
const Type &LLInterp<Type>::getStartVal() const
{
    return mStartVal;
}

template <class Type>
void LLInterp<Type>::setEndVal(const Type &end_val)
{
    mEndVal = end_val;
}

template <class Type>
const Type &LLInterp<Type>::getEndVal() const
{
    return mEndVal;
}

template <class Type>
const Type &LLInterp<Type>::getCurVal() const
{
    return mCurVal;
}


template <class Type>
void LLInterp<Type>::setStartTime(const F32 start_time)
{
    mStartTime = start_time;
    mDuration = mEndTime - mStartTime;
}

template <class Type>
F32 LLInterp<Type>::getStartTime() const
{
    return mStartTime;
}


template <class Type>
void LLInterp<Type>::setEndTime(const F32 end_time)
{
    mEndTime = end_time;
    mDuration = mEndTime - mStartTime;
}


template <class Type>
F32 LLInterp<Type>::getEndTime() const
{
    return mEndTime;
}


template <class Type>
bool LLInterp<Type>::isDone() const
{
    return mDone;
}

template <class Type>
bool LLInterp<Type>::isActive() const
{
    return mActive;
}

//////////////////////////////
//
// LLInterpLinear derived class implementation.
//
template <typename Type>
void LLInterpLinear<Type>::start()
{
    LLInterp<Type>::start();
    mCurFrac = 0.f;
}

template <typename Type>
void LLInterpLinear<Type>::update(const F32 time)
{
    F32 target_frac = (time - this->mStartTime) / this->mDuration;
    F32 dfrac = target_frac - this->mCurFrac;
    if (target_frac >= 0.f)
    {
        this->mActive = true;
    }

    if (target_frac > 1.f)
    {
        this->mCurVal = this->mEndVal;
        this->mCurFrac = 1.f;
        this->mCurTime = time;
        this->mDone = true;
        return;
    }

    target_frac = llmin(1.f, target_frac);
    target_frac = llmax(0.f, target_frac);

    if (dfrac >= 0.f)
    {
        F32 total_frac = 1.f - this->mCurFrac;
        F32 inc_frac = dfrac / total_frac;
        this->mCurVal = inc_frac * this->mEndVal + (1.f - inc_frac) * this->mCurVal;
        this->mCurTime = time;
    }
    else
    {
        F32 total_frac = this->mCurFrac - 1.f;
        F32 inc_frac = dfrac / total_frac;
        this->mCurVal = inc_frac * this->mStartVal + (1.f - inc_frac) * this->mCurVal;
        this->mCurTime = time;
    }
    mCurFrac = target_frac;
}

template <class Type>
F32 LLInterpLinear<Type>::getCurFrac() const
{
    return mCurFrac;
}


//////////////////////////////
//
// LLInterpAttractor derived class implementation.
//


template <class Type>
LLInterpAttractor<Type>::LLInterpAttractor() : LLInterp<Type>()
{
    mForce = 0.1f;
    mVelocity *= 0.f;
    mStartVel *= 0.f;
}

template <class Type>
void LLInterpAttractor<Type>::start()
{
    LLInterp<Type>::start();
    mVelocity = mStartVel;
}


template <class Type>
void LLInterpAttractor<Type>::setStartVel(const Type &vel)
{
    mStartVel = vel;
}

template <class Type>
void LLInterpAttractor<Type>::setForce(const F32 force)
{
    mForce = force;
}

template <class Type>
void LLInterpAttractor<Type>::update(const F32 time)
{
    if (time > this->mStartTime)
    {
        this->mActive = true;
    }
    else
    {
        return;
    }
    if (time > this->mEndTime)
    {
        this->mDone = true;
        return;
    }

    F32 dt = time - this->mCurTime;
    Type dist_val = this->mEndVal - this->mCurVal;
    Type dv = 0.5*dt*dt*this->mForce*dist_val;
    this->mVelocity += dv;
    this->mCurVal += this->mVelocity * dt;
    this->mCurTime = time;
}


//////////////////////////////
//
// LLInterpFunc derived class implementation.
//


template <class Type>
LLInterpFunc<Type>::LLInterpFunc() : LLInterp<Type>()
{
    mFunc = nullptr;
    mData = nullptr;
}

template <class Type>
void LLInterpFunc<Type>::setFunc(Type (*func)(const F32, void *data), void *data)
{
    mFunc = func;
    mData = data;
}

template <class Type>
void LLInterpFunc<Type>::update(const F32 time)
{
    if (time > this->mStartTime)
    {
        this->mActive = true;
    }
    else
    {
        return;
    }
    if (time > this->mEndTime)
    {
        this->mDone = true;
        return;
    }

    this->mCurVal = (*mFunc)(time - this->mStartTime, mData);
    this->mCurTime = time;
}

//////////////////////////////
//
// LLInterpExp derived class implementation.
//

template <class Type>
void LLInterpExp<Type>::update(const F32 time)
{
    F32 target_frac = (time - this->mStartTime) / this->mDuration;
    if (target_frac >= 0.f)
    {
        this->mActive = true;
    }

    if (target_frac > 1.f)
    {
        this->mCurVal = this->mEndVal;
        this->mCurFrac = 1.f;
        this->mCurTime = time;
        this->mDone = true;
        return;
    }

    this->mCurFrac = 1.f - (F32)(exp(-2.f*target_frac));
    this->mCurVal = this->mStartVal + this->mCurFrac * (this->mEndVal - this->mStartVal);
    this->mCurTime = time;
}

#endif // LL_LLINTERP_H